That's Et Legacy. The original is 2.60

He appeared in RTCW

Technically both should find the autoexec in etmain, but in practice I found this to not always be true. Putting it in every mod folder solved this f…

It should. As each mod has its own separate cfg.Perhaps, elaborate on why you think this doesn't work?

Put copies of it in your mod folders (legacy/jaymod/nitmod/etc).

You don't need Steam. Just go www.etlegacy.com